promise 执行顺序

Question

console.log('main-1')function foo(param){  var p = new Promise(function(resolve, reject) {    console.log('promise-1')    if (param === 1) {
      resolve('1')
    } else {
      reject('2')
    }    console.log('promise-2')
  })  return p
}console.log('main-2')

foo(1).then(function(value) {  console.log('then-1')
})console.log('main-3')

Answer 1

运行结果是 main-1main-2promise-1promise-2main-3then-1为什么main-3 会在promise运行之后